Epoxy Anchors

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

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An epoxy anchor is only as good as the hole, the cleaning and the cure. Follow the maker exactly.

The big idea

An epoxy anchor is a threaded rod glued into a drilled hole in hardened concrete. It is used to fix a missed or misplaced cast-in bolt, add hold-downs, and make retrofits. It works only as well as the installation: the hole, the cleaning, the injection and the cure. A Structure magazine article notes that adhesive sensitivity can be influenced by mixing, hole cleaning and moisture, so one bad step weakens the whole anchor.

What the standards say

Adhesive anchors are not a Part 9 prescriptive item. They are chosen and designed by an engineer. What I could source:

• A Hilti Canada engineering article says that, for post-installed anchors tested to ACI 355.2 and ACI 355.4, design information under the Canadian concrete standard (CSA A23.3-19, Section D.10.2.2) is taken from a product evaluation report. ICC-ES reports are based on testing to the AC308 criteria, which reflect ACI 355.4.
• The same article says to follow the manufacturer's printed installation instructions for cure times, working times and hole-cleaning methods, and recommends installer training on them.
• Structure magazine says hole cleaning has a significant impact on performance, typically blow, brush with a steel wire brush, then blow again, with requirements that vary by system. Cure rate depends strongly on temperature: common installation ranges are 41 to 104 °F (5 to 40 °C), some products are tested down to 14 °F (−10 °C), and a 24-hour cure rule of thumb may not be enough for some products. Its inspection rules for sustained overhead loads come from the US IBC, not a Canadian code.

Both sources are manufacturer or US-trade articles, so treat them as secondary. I did not verify CCMC evaluation requirements, provincial silica rules or proof-load testing rules.

Components

• Threaded rod (galvanized or stainless, as specified)
• Two-part structural epoxy in an approved cartridge
• Rotary hammer with the right bit
• Wire brush and blow-out tool (oil-free compressed air or a hand pump)
• Dispensing gun and mixing nozzle

Installing the anchor

1. Check. Confirm the product is the approved one, the concrete is old enough and within the product's temperature range, and scan for rebar.
2. Drill. Use the bit size and depth from the product instructions or the engineer. Drill straight, and keep away from rebar and edges by the distance the design gives.
3. Clean. Blow, brush, then blow again for the number of cycles the product requires, with a brush that fits the hole and clean, oil-free air. Keep dust and water out until you inject.
4. Inject. Discard the first bit of epoxy from each new nozzle until it is an even colour. Start at the bottom and back out slowly so you do not trap air. Fill the amount the maker states.
5. Set the rod. Push the rod in with a twisting motion to the marked depth and check epoxy comes up around it.
6. Cure. Do not disturb, load or tighten until cured. Cure time depends on concrete temperature, so use the maker's chart.

Example (numbers made up). A hole 150 mm (5 7/8 in) deep for each of 8 hold-down rods is 8 × 150 = 1,200 mm (3 ft 11 1/4 in) of drilling in total. Hole size, depth and cure come from the product sheet.

Common mistakes

• Poor hole cleaning
• Wrong hole size or depth
• Too little epoxy
• Rod disturbed during cure
• Non-approved epoxy
• Tightening before cure
• Hitting rebar